Bird flu, or avian influenza, is caused by influenza viruses that infect birds. While it primarily affects domestic poultry like chickens and turkeys, some strains can infect humans through close contact with infected birds. The H5N1 strain is currently a concern as it can be fatal in humans. Health organizations are working to prevent its spread and have treatment plans in place using antiviral drugs like Tamiflu. With proper food handling and thorough cooking of poultry, the risk of transmission to humans is low.